Unaweep Canyon: The Canyon With Two Mouths

Unaweep Canyon in western Colorado, the United States, is a large canyon that cuts across the Uncompahgre Plateau, a large uplift within the Colorado Plateau with an average elevation of nearly 3 kilometers. Unaweep Canyon is the only major canyon in the Colorado River drainage not occupied by a river. Instead, it is occupied by two small creeks, which flows, paradoxically, in opposite directions from a gentle divide within the canyon—the almost imperceptible Unaweep Divide. For this reason, Unaweep Canyon is said to be the only canyon in the world with two mouths.

Photo: Cook Cottage/Flickr

The two creeks, named East Creek and West Creek, flow through the canyon in opposite directions to join, respectively, the Gunnison River near the town of Whitewater and the Dolores River near Gateway. Between these two towns, the Unaweep Canyon carves a winding passage 70 kilometers long, nearly a kilometer deep and as wide as 6 kilometers at places. Because the two creeks that currently occupy the canyon are too small to have excavated such a massive pathway, geologists believe that the canyon was dug either by the Colorado River or the Gunnison River, or both, and was subsequently abandoned as the rivers took a new course. Another theory is that it was carved by glaciers, but the relatively low elevation of the canyon, and lack of Pleistocene glacial deposits, make this problematic. Yet another theory of origin states that Unaweep was a pre-existing canyon, a paleo canyon, that was only exhumed by the Gunnison River.

The canyon lies entirely on private lands, owned by a combination of a few large ranching families and private residences. During the radium boom of the early 1900s, a wagon route ran through the bed of the canyon, hauling supplies into and radium ore out of Gateway. This route later became a state highway.

Image credit: Gerilyn S. Soreghan et al.

Photo: Bureau of Land Management/Flickr

Cows on the grassland in Unaweep canyon. Photo: Serj Malomuzh/Shutterstock.com

References:
# Geology of Unaweep Canyon and its role in the drainage evolution of the northern Colorado Plateau, https://pubs.geoscienceworld.org/gsa/geosphere/article/11/2/320/132210/Geology-of-Unaweep-Canyon-and-its-role-in-the
# Summit Post, https://www.summitpost.org/unaweep-canyon/608179